It is known that either the topical application or oral ingestion of certain chemical compounds, known as furocoumarins, certain isomers of which are called psoralens, have an effect on the responsiveness of human skin to sunlight. These psoralen compounds, including 9-methoxypsoralen, which has the generic name of methoxsalen, have long been used in the treatment of certain skin diseases, such as vitiligo, which is characterized by a spotty loss of pigmentation of the skin.
The compound 9-methoxypsoralen having the structural formula ##STR1## and the chemical name 9-methoxy-7H-furo[3,2-g][1]benzopyran-7-one has been obtained from natural sources, namely from the fruit of the Ammi Majus Linn. plant, see for example, Fabmu et al., "Ammi Majus Linn. Pharmacognostical study and isolation of crystalline constituent, Ammoidin", Quart. J. Pharm. and Pharmacol., 21:449, 1948.
The present invention is drawn to synthetic processes to produce the compound 9-methoxypsoralen. The following reaction scheme represents the various process steps and novel intermediates which may be utilized to produce methoxsalen (compound of formula I). ##STR2##